1. Field of the Invention
The present invention relates to a battery module in which cooling efficiency of unit batteries is improved.
2. Description of the Related Art
A rechargeable battery module is typically formed by serially connecting several secondary (rechargeable) batteries (a individual secondary battery hereinafter being designated a “unit battery”).
Each of the unit batteries includes an electrode assembly in which a separator is interposed between a positive electrode and a negative electrode. The electrode assembly is inserted inside a container, and a cap assembly is assembled with the container to seal the container. The cap assembly may include terminals extending from the interior to the exterior of the container and the terminals may be electrically connected to the positive electrode and the negative electrode.
If the unit batteries are prismatic type batteries, the unit batteries are arranged such that positive and negative terminals of one unit battery alternate with the positive and negative terminals of an adjacent unit battery. Electric conductor adaptors are typically mounted on the negative and positive terminals such that they are electrically connected to form the battery module.
Since the typical battery module includes several to tens of unit batteries, the heat generated from the unit batteries must be efficiently dissipated. It becomes particularly important that a temperature difference between the unit batteries of the battery module must be minimized regardless of their locations. The heat dissipation property of the battery module is a very important factor on which the performance of the battery module depends.
When the heat dissipation is not properly realized, a temperature difference between the unit batteries may be generated which deteriorates the charge/discharge efficiency. Furthermore, the temperature of the battery module may increase excessively, thereby deteriorating the performance of the battery module or, in the most severe cases, causing an explosion of the battery module.
Particularly, when the battery module is used as the high capacity secondary battery for driving motors of, for example, a vacuum cleaner, an electric scooter, or a hybrid electric vehicle, the charge and discharge is done with a large capacity of current. Thus, the internal temperature of the battery module increases excessively. This deteriorates the inherent performance of the battery module. Therefore, it becomes very important to efficiently dissipate the excessive heat out of the battery module.